1. Field of the Invention
The present invention relates generally to the field of medical devices. In particular, the present invention relates to long term, implantable devices that permits access to inner physiology and that enable non-traumatic removal following treatment.
2. Summary of the Related Art
Medically treating a patient often requires long term placement of a medical device across one or more organ systems to establish access to a specifically targeted interior body site for diagnostic or therapeutic purposes. One common example is the establishment of percutaneous vascular access for purposes of administering liquid therapeutic agents, removing bodily fluids for testing or monitoring, treating bodily fluids before being returned to the body, and/or disposing of bodily fluids.
Particularly in the case of administering fluids to the body or removing fluids from the body continuously or periodically over an extended time period, those skilled in the medical arts typically use what are known as “permanent” catheterization techniques. These techniques employ implanted devices such as tunneled central venous catheters (CVCs) that remain implanted for durations ranging from a few weeks to years. Examples of such implanted and related medical devices exist in the following references, which are incorporated herein by reference: U.S. Pat. No. 4,266,999 (Baier); U.S. Pat. No. 4,405,305 (Stephen et al.); U.S. Pat. No. 4,488,877 (Klein et al.); U.S. Pat. No. 4,668,222 (Poirier); U.S. Pat. No. 4,897,081 (Poirier et al.); U.S. Pat. No. 4,935,004 (Cruz); U.S. Pat. No. 5,098,397 (Svensson et al.); U.S. Pat. No. 5,100,392 (Orth et al.); U.S. Pat. No. 5,242,415 (Kantrowitz et al.); U.S. Pat. No. 5,662,616 (Bousquet); U.S. Pat. No. 5,823,994 (Sharkey et al.); U.S. Pat. No. 5,830,184 (Basta); U.S. Pat. No. 5,848,987 (Baudino et al.); U.S. Pat. No. 5,882,341 (Bousquet); U.S. Pat. No. 5,989,213 (Maginot); and U.S. Pat. No. 6,033,382 (Basta). Examples of therapeutic regimens requiring such long-term continuous or periodic access to a specific internal body location include parenteral feeding, chemotherapy, antibiotic administration, dialysis, and chronic anesthesiology. Central catheterization for these types of procedures are discussed in “Vascular Access for Oncology Patients” (Gallieni et al, CA Cancer J Clin 2008 doi: 10.3322/CA.208.0015).
Generally, the type of procedure that a patient requires dictates whether a physician will utilize an acute, short term catheterization technique, or a chronic, long term catheterization technique. For example, establishing a state of general anesthesiology in preparation for a surgical procedure typically involves placing a CVC in a patient's blood vessel for a relatively short period of time, such as a few minutes to a few hours, and then removing the catheter once the surgery is finished and the patient is revived. When performing such an anesthesiology procedure, a physician commonly uses a short term catheterization technique to place a drug delivery catheter in a blood vessel of the patient.
In direct contrast to this example of short term CVC placement, a physician performing a hemodialysis procedure in a patient suffering from chronic kidney failure may place a CVC in one of the patient's blood vessels for a relatively long period of time. Such a patient typically requires dialysis sessions three times per week for an indefinitely extended period of time. Healthy kidney function ensures removal of fluid, chemicals, and wastes typically filtered from a person's blood. Hemodialysis removes these elements by sending a patient's blood to an external artificial kidney machine via the permanent vascular access, often established by placement of a long term catheter within the patient. A patient who is involved in such a hemodialysis regimen may need a catheter placed in a blood vessel for weeks, months, or years in order to provide a ready means for vascular access into that patient's bloodstream to enable these frequent life saving dialysis treatments.
Long term catheterization techniques typically entail inserting a catheter into a patient using a “tunneled catheter technique.” This procedure involves inserting a long term catheter into the patient through an incision in the skin and then routing the catheter for several centimeters under the skin before entering deeper regions of the body. Despite routine use, conventional tunneled catheter designs seriously compromise the ability of a patient's skin to protect the patient's body from infection. As discussed in “Intravascular Catheter-Related Infections: New Horizons and Recent Advances” (Raad et al., Arch Internal Medicine/Vol 162, Apr. 22, 2002, Pages 871-878.), catheter-related infections are frequent events and present a potentially fatal health problem. High morbidity rate and high procedural cost are characteristics of typical long term tunneled catheter usage. The primary reason that the use of conventional catheters leads to a high rate of infection is that microorganisms enter the body through the skin incision. A conventional tunneled catheter device may include a cylindrical tissue ingrowth cuff that acts as a barrier for micro-organisms entering the body and that anchors the catheter in the subcutaneous tunnel. Such a conventional device, however, still fails to prevent undesirably high infection rates. This is because standard cuff designs are designed for positioning within a subcutaneous tunnel rather than at the skin entry site, which is the most effective location at which to position a tissue ingrowth cuff for preventing infection.
Another conventional tunneled catheter design is entirely subcutaneous. This embodiment provides an advantage over traditional transcutaneous tunneled catheter designs by eliminating the need for a continuously maintained breach in skin and thereby reducing risk of infection. These subcutaneous catheters are connected to a port disposed beneath the skin. The port is capable of accepting a needle injection of fluid and then providing fluid to the subcutaneous catheter. The port has a compressed rubber septum on its upper surface immediately below the skin which is adapted for receiving a needle therethrough and resealing under residual compressive forces once the needle is removed. These fully subcutaneous devices present drawbacks relative to conventional transcutaneous catheter systems. Particularly, large bore needles would irreparably damage the septum, and so usage is limited to procedures that require low flow rates. An example of such an implanted, subcutaneous port and catheter device is provided in U.S. Pat. No. 5,562,618 (Cai, et al).
Some transcutaneous tunneled catheter devices include adjustable epidermal tissue ingrowth cuff assemblies that enable skin to heal into the devices at their entry sites into the dermis. Such devices provide reduced risk of infection, and because they require no needle punctures for gaining access to the catheter, these assemblies enable the higher flow rates associated with conventional transcutaneous tunneled catheter designs. For example, the apparatus and methods disclosed in U.S. Patent Application No. 2004/0236314 to Mark A. Saab (Saab), incorporated herein by reference, allow a physician to place a modular dermal tissue ingrowth cuff assembly precisely within a skin incision site and subsequently adjust the location of the distal (internal) tip of a catheter assembly associated with the tissue ingrowth cuff assembly. This device comprises a base (or port) having tissue ingrowth material thereon for securely anchoring the port at the incision site. A physician using such a device, therefore, has the ability to position the catheter tip precisely at the desired body site without disturbing, moving, or stressing the fixed tissue ingrowth cuff. Positioning the modular tissue ingrowth cuff at the skin incision site enables the skin to heal into the device and regain its ability to protect the patient from infection.
The use of a port with a transcutaneous catheter and skin tissue ingrowth cuff assembly has resulted in numerous improvements related to patient care and well being, but they do not anticipate or address the issue of simple and efficient removal of the port once the therapy has been completed and the device is no longer needed. U.S Publication Number 20070043323 to Davey and U.S. patent application Ser. No. 11/986,451 also to Christopher Davey address systems and methods for facilitating removal of subcutaneous tissue ingrowth devices. (Both of these references are incorporated herein by reference). The teachings in these references address the problem of tissue becoming too firmly ingrown into tissue ingrowth scaffolds, thereby requiring blunt dissection of the tissue from the device. The inventions of the Davey references comprise tissue ingrowth scaffolds that are at least partially bioabsorbable material and/or detachable from the device so that the scaffolds remain behind when the port is removed. These easily removed devices nonetheless require that a physician create a large incision through the skin to facilitate removal of the subcutaneous implanted device, regardless of the scaffold design or material. The need to make a large incision to enable removal of the subcutaneous implant significantly prolongs the procedure, greatly increases trauma to the patient, and exposes the patient to another risk of infection as a result of the added extensive breach to the skin.
A need therefore exists for a subcutaneous port that anchors a transcutaneous conduit during a treatment period and then enables removal through a minimally sized incision in the skin that causes little or no additional trauma to the patient.